Device for measuring and comparing functions



Nov. 1'4, 1950 A. CHEVALLIER mzvzcz: FOR MEASURING AND COMPARING FUNCTIONS Filed April 5, 1945 4 Sheets-Sheet 1 w u n ATTORNEK? Nov. 14, 1950 r A. CHEVALLIER 2,529,723

DEVICE FOR MEASURING AND COMPARING FUNCTIONS Filed April 5. 1945 4 Sheets-Sheet 2 mum INVENTDR ATTORNEYS Nov. 14, 1950 A. CHEVALLIER DEVICE FOR MEASURING AND COMPARING FUNCTIONS 4 Sheets-Sheet 3 Filed April 5, 1945 IIyVENTOR 1474*? (flaw/liar BY fiawazffli ATTORNEYS Nov. 14, 1950 A. CHEVALLIER 2,529,723

DEVICE FOR MEASURING AND COMPARING FUNCTIONS Filed April 5, 1945 4 Sheets-Sheet 4 INVENTUR ATTORNEYS Patented Nov. 14, 1950 DEVICE FOR MEASURING ANDCOMPARIN G FUNCTIONS Andr Chevallier, Paris, France, assignor to Socit Union DElectricite, Paris (Seine), France,

a society of France Application April -5, 1945, Serial No. 586,778 In France April 14, 1942 Section 1, Public Law 690, August 8, 1946 Patent expires April 14, 1962 2 Claims. (01. 172-245) My invention relates to apparatus for comparing the phases of two sinusoidal factors of the same frequency. The invention is more especally, although not exclusively, concerned with telecontrol devices of this kind used for the discriminative protection of electric distribution systems or in connection with other remote control systems.

The object of the present invention is to provide apparatus of this kind which are better adapted to meet the requirements of practice than those used fcr the same purpose up to the Figs. 2 and 3 are two diagrams of comparator devices made according to two embodiments of my invention;

Fig. 4 shows the current-voltage curve of a contact rectifier, this curve being given to illustrate the working of rectifiers such as those shown by Figs. 2 and 3;

Fig.5 is a diagram given for the same purposes;

Figs. 6 and 7 show modifications of the diagram of Fig. 3;

Fig. 8 is a general diagram of the protection apparatus to be provided at a section end, this apparatus making use of comparator devices ac.- cording to the invention; 7

Fig. 9 diagrammatically shows a system for measuring or recording, eventually for tele-regu lation purposes, the phase difference angle existing in voltages or currents on the input and output side of two stations of an-energy distribution system, according to the invention;

Fig. 10 shows an arrangement according to the present invention for discriminative protection purposes;

Fig. 11 diagrammatically shows a voltage limiting device to be included ina system according to the invention;

- Fig. 12 is a diagram of the voltages on the input and output sides of this limiting device.

In the following description, it will be supposed that the invention is applied to the protection of an energy transmission network.

In Fig. 1, I have diagrammatically shown, by way of example, a line L supposed to be fed at both ends by groups of machines MlM2. Several sections are illustrated at AB, CD, EF, with their circuit-breakers d1, di, dz, d'2, d3, ds, etc, which are associated with devices capable of either releasing them or, on the contrary, locking them, this under the direct or indirect action of directional relays influenced by the direction of the defect currents, or fault currents.

It, is known that a fault acts to cause, at the ends of above mentioned sections, currents and voltages to appear, the directions of which are determined by the location of the fault.

If a fault occurs, for instance, at T, in section CD, the currents i1, 2"1 in section AB remain in phase, same as the currents i3, is in section EF, while the currents 2'2, 1'2 in the section CD where the fault has occured are reversed with respect to each other. The object of my invention is to provide devices for comparing the voltages at suitable points of the system to control the release or locking of the above mentioned circuit-breakers.

These comparator devices are constituted by rectifiers of the contact type, arranged to discriminate, when a fault occurs, what protection apparatus (in the application of my invention that has been considered up to now) are to be released or operated. In these arrangements, I may make use either of the curvilinear portion or of the rectilinear portion of the current-voltage characteristic curve (Fig. 4) of the rectifiers.

.In the first case, in which the current rectification law is expressed by: y kv means are provided for obtaining, in suitable rectification circuits, currents of the following form:

j=k(dt' -bu) ;i'=k(buai) from which, by subtraction, I obtain a function:

r :4 kabui which represents a modulation, as in the preceding case.

Fig. 2 illustrates an arrangement correspondingto this. For this purpose, I make use of at Ui bu. The four other windings a, b, c, d (prefe erably identical and wound in the same direction) constitutes the secondary and are intended 4 circuits are connected with resistance p1 and p2, and I thus obtain, between points a and b a voltage m which, in this case also, is impressed on two tubes 21 and 12. The relays for controlling the circuit-breakers are visible at Rd and Rv. The operation is the same as that of the apparatus of Fig. 2.

I may also, as shown by Fig. 6, provide only one release relay Rd, in which case I employ only one tube Z connected to the ends a and b of the resistance.

Capacities may be provided, as shown at C across the terminals of 1 (Fig. 6) to permit of adto be respectively connected to corresponding rectifiers or systems of rectifiers 2! to 24, and

also to the secondary windings of the element s'of 4 the second transformer.

The latter is preferably made of two distinct elements T2 and T3, each of which includes three windings, to wit: A, a, b and A", a", 1). Windings A and A" constitute the primaries and are, fed with the voltage U2=ai, but in phase opposition. Windings a, b and a, b constitute the secondaries. They are also, for each transformer, mounted in phase opposition, as shown by the drawing. h

The rectifiers are mounted in such manner that, in each half corresponding to one of the elements T2 or T3, the two rectifiers 2l'22 or 23-2.! are fed in opposite directionsthe current therefore flowing alternately only through one of the two. 1

It will be readily understood that one of the halves performs the addition ai-l-bu and the other the subtraction bu-ai. Therefore, I obtain in this way a currenty" of the form above set forth, which current can be either utilized directly, or transformed into a correspondingdirect'voltage, for instance by making use of suitably connected resistances, such as t1, t2'this voltage to being obtained between two terminals such as G and H on the drawing. Ifit is supposed that the values of resistance t1 and 152 are both equal to r, I obtain at said terminals the following voltage: f

which is a direct voltage, positive if "U1 and U2 are in phase (that is to say if U and I are in phase), equal to zero if the phase difference of U and I is 90, and negative if this phase differerence is 180.

Control of the protection aparatus (circuitbreakers or the like) in response to variations of sign of this voltage will be performed through any suitable relays, with or without amplification. The whole is, for instance, adjusted in such manner that', as soon as a voltage "10 appears and according as point H is positive or negative with respect to point G, either one or the other of relays m m is energized, I I i 'The sa me apparatus might, of course, be acted upon by several symmetrical components.

Fig. 3 shows a comparator device of the contact rectifier type particularly'well (but not exclusive- 1y) adapted to be utilized onthe rectilinear portion of the characteristic curve. Generally speaking, the diagrams are, in this case, of the same kind as those of Fig; 2, butsimpler'. The alternating voltages uiand m are added together in the upper circuit of said Fig. 5 and subtracted from each other in the lower circuit, "owing to the provision of suitable transformersonly the secondaries of whi'ch are shown on the drawing, The rectifiersareshown at r1, r rs, m. "The justing the time constant to a minimum and thus to ensure the highest possible speed of operation. I mayalso, in order to reduce the value of this time constant, insert the release coil bi directly in the tube circuit (Fig. 7).

In Fig. '7, which shows an embodiment in which I make use of a thyratron, reference character Pdesignates the grid polarization battery, provided with a resistance r. The anodic circuit includes a switch for cutting the current therethrough after release of the circuit-breaker, for instance operative by the latter.

It is interesting to explain why the arrangement of Fig. 5 works correctly in the case of operation along the straight portion of the characteristic curve (values of it higher than uo, Fig. 4). This results from the fact that the mean current flowing through resistances p1 and p2 is given by the following formula:

j...=[-/ 1 2 +2U1U2 cos 'VU1Z+UQZ2U1UZ COS rp] Nowjth is is aperiodic function, the period of which is 211-. Therefore, if (p is changed into vri-i-go, the sign .of the function is inversed and a'm becomes a'm.

Thus, it is found that the dry rectifier comparator devices according to the invention can work, according to'the case, either alongthe straight portion or along the curved portion of the characteristic curve. In both cases the same result is obtained to wit the mean current in. is reversed under the effect of the reversing of only one of the two voltages in and a2. Besides, it should be noted that if both of these voltages change of sign (Fig. 5), the angle between these voltages remains equal to o, so that the direction of the mean current is not modified. It should also be noted that the more or less complicated form of voltages m, m is without influence upon the result obtained, since the Fourier series de velopement of the function that represents the rectified current shows that there remains, after this rectification, in addition to the constant term (meanvalue im) only terms in Zwt, 4wt, etc., the mean value of which-from zero to 1r is zero.

In Fig. 8, by way of specific example, I have grouped the essential devices above described which are to be provided on one of the'apparatus 'at 'the endof a section, The voltage and current transformers are shown at 4 and 5. Reference numerals 6 1 designate the devices for filtering the symmetrical components. 8 is the comparator device as above described. m andm are the contact relays above described, and 9 is a starting relay. Relays m and m are supposed :tojact' o'n'thedevices or groups of devices I'll- H throughothencontact relays l2and l3. 4 v Insuch a system, in order to permit of fixing the point "of operation oathe-characteristic curve (Fig. 4), it is of interest to keep factors'i'and 1 within given limits. 'W ith' the comparators according to my invention, the only important requirement is to obtain the direction, or sign, of the product of the factors-that act upon the comparator elements relays (in the present case u and i), (and not, as it was the case with electronic wattmeters as used at the present time, to measure the value of this product). Therefore, according to my invention, I provide, between filters 8 and l and comparator 8. devices. of any conventional type, for instance (such as comparators) 14 and I for ensuring this result.

Anyway, the various features above described permit of obtaining a selective or discriminating protection system which requires but a small amount of power, as compared with that required by electro-dynamic relays which gives rise to no self-inductance component (since the voltages can be collected directly at the terminals of the resistances), the inertia of which is substantially zero (so that its action is extremely quick), and which may give any desired sensibility, with the adjunction of I amplifiers.

Besides, it should be noted that the selective, or discriminating, protection of electric networks has been considered merely by way of example. It should be well understood, in particular, that the sine functions that are considered, instead of corresponding to a current and a voltage, might represent any factors whatever (for instance two voltages or two currents), so that the invention may have many different applications, and, in particular:

Other embodiments of my invention will now be described.

According to one of these embodiments, the relays in question are utilized for comparing the respective phases of two currents or two. voltages (or a current anda voltage) at any two points of an electric distribution system, in order to permit any desired regulation.

For instance, it is possible, according to the present invention, to record at any time the angular lag of the current or voltage along a line connecting, for instance, two stations S1 and S2 of an electric network (Fig. 9).. 1

For this purpose it suffices .to provide at one of the stations, for instance S2, an apparatus such as 8 according to the invention (Fig. 9) and to impress thereon two voltages U1 and U2 the phase angles of which correspond respectively to those of said stations, the voltage U1 that corresponds to station S1 being transmitted through any suitable means, for instance through carrier currents. Apparatus 8, acting as a phasemeter, then gives at the output end thereof, in a circuit 25, a direct current the value of which measures the desired angle of lag, and which is eventually utilized for suitable regulations.

I have shown at 21 and 28 the voltage or current transformers that deliver the voltages U1 and U2 to be impressed upon apparatus 8. Voltage U1 is transmitted through carrier waves, by means of transmitting and receiving apparatus 29 and 30.

For the discriminating protection of electric networks, I preferably make use, instead of relays of the wattmetric type as employed in the preceding embodiments, of other kinds of relays, for instance of the amperemetric, voltmetric, or or analogous type, making or not use of the symmetrical components of the current.

An advantageous arrangement consists in applying the apparatus according to the invention to protection systems in which advantage is taken of the hase reversing that takes place, when a fault occurs, between the currents flowing'at the ends of the section in which the fault has .occurred. These apparatus will then act as phasemeters, in a manner analogous to that already illustrated by Fig. 9.

By way of example, I have shown on Fig.110 a device of this kind. A line section is illustrated in this drawing, with its end circuit-breakers PP', to be controlled by the protection system, the three cut-off elements of each circuit-breaker being operable separately. The electronic apparatus according to the present invention are respectively inserted in the three phases, at 818z'-8s for one end of the section and 8'1-82-8'3 for the other end. They are fed, on the one hand, with voltages prop'or tional to the currents flowing through the phases at the corresponding end of the section,and, on the other hand, with voltages proportional 'to the currents flowing through the phases at the other end, the latter being transmitted through carrier currents. v

For this purpose, the current transformers 3 1-3 I permit of obtaining currents i1-iz'i3 and i1-i'2i'3 of the same respective phases'as-the currents I and I that pass through the line, said currents being in turn transformed, through resistances or other suitable means 34-34, into voltages e1ez etc, themselves in synchronism. adapted to be fed to said apparatus. These voltages are transmitted from one end of the line section to the other end-through carrier waves by means of the usual transmitting and receiving apparatus ER-E-R, on three different modulation frequencies fi-fz-fs, also synchronous, and obtained in any suitable manner (for instance: respectively 50, and periods, these values being given merely by way of indication), these apparatus being coupled to'the line at 32-32. Volume control or other devices I 4-5 are provided at the input end of apparatus 8 81, etc. 'Finally, the direct voltage supplied by these apparatus controls the apparatus 3333' adapted to actuate the cut-off elements of circuit breakers PP', etc. in a suitable manner:

It will be readily understood that, in the ab sence of a fault, the currents II on any of the phases are in phase or, at least, have a constant phas difference with each other, so that the corresponding apparatus 8 or 8" are themselves fed With voltages of the same phase and therefore exert no action on the corresponding apparatus 33--33. i

If, on the contrary, a fault or short-circuit takes place, for instance on phase I, the corresponding end currents I1 and I'i which were initially of the same direction are now out of phase by This immediately produces the operation of the correspondingapparatus 81 or 8'1 and 33 or 33, which ensures the automatic release of the circuit-breakers of said phase.

As soon as the fault has disappeared, the initial conditions are restored and the circuitbreakers are reengaged in closing position, in an automatic manner, as known. The system constitutes by itself, due to its very principle, a phase sorter (since the three elements of each circuit-breaker are controlled separately, only that or those correspondin to the phase or phases concerned by the fault being operated).

According to my invention I make use of voltage limiting devices interposed on the input side of the comparator devices as above indicated. If

7 it is true that the quickness of release is proprtional:to.the mean current rectified in the comparator devices, whichicurrent is a function of voltages m and 112, which themselves increase simultaneously with currents I1 and 12,113 is however necessary to limit these voltages tov suitable values.- It ispossible to make use for this'purpose ,of limiting devices of any known type, provided that their time constants are as low as possible. r

For instance, it will be advantageous to make use of a device of the kind of that of Fig. 11, in which, in order to obtain a reduced voltage u: from a voltage u, I make use of rectifiers such as (11,112, arranged in parallel.

Fig. 1-1 shows that the source S that supplies voltage u feeds resistancesv R1 and R2 (R2 representing the utilization resistance) with, in shunt, rectifiers d1 8.1111112 the current-voltage characteristic curve of which is parabolic. Therefore, the resistance of these rectifiershas a curve of hyperbolic shape, that is to say decreases simultaneously with the voltage at the terminals. Under these conditions, the drop of potential across resistance R1 increasesmuch more rapidly thanthe value of voltage Besides, it should be notedthat'this drop of potential is the greater as the value of the resistances of rectifiers di and (Z2 is smaller.

Finally, I obtain, for the utilization voltage 1L1, a curve of the shape of that shown at F on Fig. 12 (where F represents the initial voltage u) It should be noted that the flattened curve F that is thus obtained may be considered as the sum of sine curves the frequencies of which are t, 2t, 3t, 4t, etc., but in which the rectifying effect has'eliminated all odd numbered harmonics. Therefore, there remains only even-numbered harmonics which, as above stated, are without influenceon the comparator device, since their mean value in a half-period is zero.

In a general manner, while I have, in the above description, disclosed what I deem to be practical and efiicient embodiments of the present invention, it should be well understood that I do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the present invention as comprehended within the scope of the appended claims.

What I claim is: 1. A phase comparator for two sinusoidal voltages both of the same frequency which comprises, in combination, two full-wave rectifier units including each at least one resistance and two contact. rectifiers having each its output connected with, the same end of said resistance so as to ,pass both of the rectified currents from said rectifiers respectivelyin the same direction through said resistance, voltage limiting means for. transforming each of said sinusoidal voltages into a sinusoidal voltage in phase therewith but of constant amplitude, means for impressing on the two rectifiers of one rectifier unit a current proportional to the sum of saidconstant amplitude voltages and on the two rectifiers of .the other rectifier unit a current proportional to the difierence of said last mentioned voltages, one of the rectifiers of each rectifier unit being arranged to pass one alternation and the otherthe other'alternation' of the current imparted to said unit, one or said resistances having one end thereof connected with one end of the other, the two other ends of said resistances being-connested-to corresponding sides of said rectifiers so as to obtain across the ends of the whole of said two resistances in series a voltage equal to the difference of the respective voltages supplied by said rectifier units, an output circuit connected acro'ss'said terminals and indicator means in said output circuit for giving the value of the constant voltage corresponding to the power factor in said output circuit.

2. A comparator according to claim 1 in which both of said rectifier units are identical and said resistances are of the same value.

ANDRE: CHEVALLIER.

REFERENCES CITED I} The followingreferences are of record in the file, of this patent: Y

UNITED STATES PATENTS 2,381,527 Traver Aug. 7, 

